Structural Optimization of Natural Plant Products: Construction, Pesticidal Activities, and Toxicology Study of New 2-Isopropanol-4-methoxy-7-alkyl/aryloxycarbonyl-(<i>E</i>)-vinyl-2,3-dihydrobenzofurans

Recently, the structural optimization of natural bioactive products has been one of the important ways to discover new pesticide candidates. Based on osthole as a lead compound, herein, a series of new 2-isopropanol-4-methoxy-7-alkyl/aryloxycarbonyl-(<i>E</i>)-vinyl-2,3-dihydrobenzofuran derivatives were synthesized. Steric configurations of compounds <b>3</b>, <b>4</b>, <b>6</b>, <b>9</b>, <b>11</b>, <b>29</b>, and <b>31</b> were confirmed by X-ray monocrystallography. Notably, an efficient method for preparation of 2-isopropanol-2,3-dihydrobenzofurans from osthole by the epoxidation and rearrangement reactions was developed. Against <i>Plutella xylostella</i> Linnaeus, compound <b>31</b> (<i>R</i> = CH₂CH₂Ph; LC₅₀: 0.759 mg/mL) displayed a 1.9-fold insecticidal activity compared to that of osthole; against <i>Tetranychus cinnabarinus</i> Boisduval, compound <b>34</b> (<i>R</i> = (CH₂)₉CH₃; LC₅₀: 0.401 mg/mL) exhibited a 3.3-fold acaricidal activity and good control effects compared to those of osthole. By the scanning electron microscope (SEM) imaging method, it was demonstrated that the acaricidal activity of compound <b>34</b> may be related to the damage of the cuticle layer crest of <i>T. cinnabarinus</i>. Compound <b>34</b> could be further studied as a potential acaricide.